This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. This project will use x-ray crystallographic studies to determine the three dimensional structures of cell surface protein complexes, which activate immune responses. Structural analysis of these complexes will provide new information on cellular activation and may lead to novel strategies to control immune pathology.